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NoShortcuts
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Group: Forum Members
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Hoosier Hurricane (8/15/2014)
.002 undersize bearings would be in order if you can find them. Did you check rod bearing clearances also. They may have been polished too much also.
Rodger, per John's suggestion for main bearings... eBay listing of .002 undersize main bearings Perfect Circle manufacturer, made in U.S.A. 2 sets presently available search eBay for item number 331039558951 Buy-It Now price - $79.95 says free shipping, but check the particulars on this...
eBay seller seems to have a good transaction record score...
a.k.a. Charlie Brown
near Syracuse, New York
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2721955meteor
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the dyno man has a set of.002mains,unless he has used them.
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RodgerF
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I didn't check the oil pump but I've tried 2 new ones, both with the same results. Tee Bird Products show bearings in .001 and .002 oversize so I may try that next. I didn't check the rods but should have. When I pulled a main and saw the scuffing, I figured I had it solved. Next time I will pull a rod cap too, just to see what they look like. I really don't want to pull the engine again so I hope I can get it fixed. All part of playing around with old cars I guess. On the other hand, I bought a new GMC truck that seems to run just about as well!  Thanks again, Rodger
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NoShortcuts
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You've GOT to be frustrated, Rodger. While .0035 is 'big', you should have more oil pressure than what you're reporting.
Did you have an opportunity to check the clearances and by-pass pressure relief mechanism in the oil pump? No problem with the oil pick-up tube fitting up and seating in the oil pump... no distortion of the tubing where the neoprene seal fits that goes into the pump housing? IF the oil pump checked out okay, my thought would be to pressure feed the oil system to do a leak down test with the oil pan off. As you've said, you're losing pressure somewhere... IF it's not at the main bearings, it would seem logical to suspect a rod bearing or cam bearing... Oil flow to the rockerarms is restricted by design... Oil flow from the rod bearings is restricted by the squirt holes in the rods that face the camshaft... I'm drawing a blank on anything else that is pressure fed where clearance would be an issue...
a.k.a. Charlie Brown
near Syracuse, New York
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Hoosier Hurricane
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Group: Moderators
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.0035 is too much clearance. .002 undersize bearings would be in order if you can find them. Did you check rod bearing clearances also. They may have been polished too much also.
John - "The Hoosier Hurricane"
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RodgerF
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Group: Forum Members
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Thanks for the suggestions. Using the red plastiguage I had a clearance of .0035 with new bearings. We rolled the new bearings in primed the engine and everything looked good. Initial startup with 20w-50 gave right at 60 psi but pressure started to drop as the temp came up. Put maybe 10 miles on the car and by the time we got back had around 5 psi at idle and an audible knock from the crank just like before.
Is that too much clearance? Should I have went with the .001 or .002 oversized bearing? Anything else that can cause a drop in pressure like the cam bearings or something? Maybe I can talk Mr. Mummert into selling me one of his engines!
Thanks again,
Rodger
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NoShortcuts
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Hmmmm... GooD point!
I've only used Plastigage for checking engine bearings when an engine has been bottom-side up, i.e. with the oil pan up.
Thanks for correcting my suggestion. 
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York
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2721955meteor
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if you are checking clearance in the car,install cardboard in2 mains along side one to be checked snug them up and check others (you need the crank sucked upto get a acurate clearance)
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NoShortcuts
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From what you've said, when the oil is cold you've got some pressure, Rodger. When the engine is up to operating temperature and the oil viscosity changes, the pressure is lost.
No argument that clearances someplace are likely the issue. Consider checking the clearances in your oil pump, too, even if it is 'NEW'... and check the oil pressure relief valve mechanism.
Let us know what you find as you work through this.
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York
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NoShortcuts
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Group: Forum Members
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Hmmmm... Consider using Plastigage (red 0.002-0.006) to do a quick check on the main bearing clearances before pulling EVERYTHING apart to use the micrometer... 
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York
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